DIRECT ESTIMATION OF VOLUMES IN OVARIAN FOLLICLES USING THE NUCLEATOR

The aim of the study was to evaluate the precision of the nucleator pr inciple with regard to estimation of follicle, oocyte and antral volum es in individual follicles, as well as their average volumes in a grou p of follicles. Nine isolated murine ovarian follicles embedded in pla stic were orientated isotropically, cut into 20 Irm serial sections, a nd stained with hematoxylin. In each follicle the volumes of the folli cle, the antrum and the oocyte were estimated in two ways, both unbias ed: Firstly, in just one unique section through the follicle, viz. the section which contains the unique sampling point - the nucleolus of t he oocyte - using the nucleator principle, and, secondly, in the compl ete set of follicle sections using the Cavalieri principle. Estimates using the Cavalieri, which are very precise (CE(Follicle)similar to 0. 03, CE(Oocyte)similar to 0.11, CE(Antrum)similar to 0.16), were interp reted as the ''true'' values. Therefore, the precision (estimator vari ation) of the nucleator estimates could be calculated. The nucleator e stimates correlated well with the Cavalieri estimates: r(follicle)=0.9 5; r(antrum)=0.88; r(oocyte)=0.83. The nucleator provides very precise estimates of the volumes of follicle, oocyte and antrum with a minima l amount of effort, since the estimates are derived from measurements in only four directions sampled in a uniform systematic way, the first direction being chosen at random, in only one section through the fol licle. Moreover, it is not necessary to know the precise thickness of the section, and, finally, the estimates are expressed in correctly di mensioned terms. The estimator variation of the nucleator (CE = 0.28) is of minor importance compared to the biological variation (CV = 0.47 ) in this realistic sample of follicles.